The present invention relates to a swivel connection for the regulation of air pressure in a tire assembled on a rim of a vehicle wheel while the vehicle is in traffic comprising a first ring-shaped member fixedly connected with the rim and rotatable with the wheel of the vehicle when rotating around its hub, and a second ring-shaped member that does not rotate relative to the hub and that interacts with the first ring-shaped member. A ring-shaped duct is formed between the first and the second ring-shaped member and which duct is connected with the inner air-space in the tire and an air-pressure unit for regulation of the air pressure in the tire both when the vehicle is moving and when it is not moving.
Correct tire pressure is and has been important for road holding abilities. To change the tire pressure in the conventional way, that is to increase the air pressure by means of a stationary air compressor or to deflate the tire manually is not a practical way when the need for pressure regulation changes at short intervals. Several solutions to solve this problem therefor have been presented. Here it is assumed that the wheel is rotating on a hub having bearings and encloses a driving axle for the wheel. Those solutions have in common that a swivel connection is arranged in connection with the hub and compressed air is fed into the tire or the tire is deflated via a duct in the hub that is in connection with a ring-shaped duct extending between the hub and the rim that carries the tire. The hub and rim therefor have to be provided with this swivel connection already when constructing the wheel system. Examples of such contructions are known, e.g., from U.S. Pat. Nos. 3,705,614 and 5,203,391. A solution that differs somewhat from those is known from U.S. Pat. No. 2,017,158 where the wheel is fixedly assembled on an axle that in turn is rotary in a bearing and where the swivel connection is arranged between the hub and a brake drum belonging to the wheel.
None of the known solutions enables the swivel connection to be assembled afterwards on a vehicle wheel nor do they admit that the movement of the wheel differs materially from its ideal travel.
The object of the present invention is to achieve a swivel device to be assembled afterwards on different types of vehicle wheels and which enables regulation of the tire pressure even when the vehicle is moving and that is insensitive to deviations from the ideal rotation of the wheel, that is, insensitive to a possible eccentricity in the movement of the rim or deviation from the ideal plane of rotation transversely to the direction of axis of the hub. The object is achieved with a swivel device according to the present invention wherein the second ring-shaped member is connected with the first ring-shaped member via a bearing and is prevented from rotation around the hub by means of a holder fixed to the vehicle. Preferably the holder is elastically connected with the second ringshaped member in order to be able to take up the mentioned deviations in the rotation of the wheel. The holder is assembled on the hub by means of a clamping device that is adaptable for different types of hubs. The first ring-shaped member may be rotary in relation to the second ring-shaped member, for instance via a ball bearing comprising balls that are held apart by distance members. The two interacting rings in this embodiment are held together by means of a clamp ring that also is part of the bearing race of the ball bearing. On each side of the fixed ring and spaced radially from one another are seal joints to prevent dirt and water from penetrating into the ball bearing.
In a preferred embodiment, the first ring-shaped member is a rotary ring having a U-shaped cross section that forms a ring-shaped duct, which is open in a direction towards the vehicle chassis and that is connected with the tire via a conduit, and the second ring-shaped member is a fixed ring arranged in the duct and sealing it. A conduit for feeding compressed air to raise the tire pressure or for deflation in order to lower the tire pressure is connected with a case that is arranged on the second ring-shaped member and is connected with an air duct that extends through the second ring-shaped member to the ring-shaped duct. The feed duct ends in a ring-shaped slot in the second ring-shaped member which carries a ring-shaped seal that extends into the ring-shaped duct. The seal is provided with circumferentially equally spaced holes through which air can pass to the ring-shaped duct.
It lies within the scope of the invention to vary the embodiment of the two ring-shaped members within broad limits. For instance, the ring-shaped duct may be formed in the second, fixed ring-shaped member instead of in the first, rotary member. The holder that prevents the rotation of the second, fixed member may be placed on other parts of the vehicle chassis than the hub.
Further features and characteristics concerning the present invention are evident from the description of the drawings below and from the claims.